Types and Values

Includes

#include <gdk/gdk.h>

Description

In addition to the normal keyboard and mouse input devices, GTK+ also
contains support for extended input devices. In
particular, this support is targeted at graphics tablets. Graphics
tablets typically return sub-pixel positioning information and possibly
information about the pressure and tilt of the stylus. Under
X, the support for extended devices is done through the
XInput extension.

Because handling extended input devices may involve considerable
overhead, they need to be turned on for each GdkWindow
individually using gdk_input_set_extension_events().
(Or, more typically, for GtkWidgets, using gtk_widget_set_extension_events()).
As an additional complication, depending on the support from
the windowing system, its possible that a normal mouse
cursor will not be displayed for a particular extension
device. If an application does not want to deal with displaying
a cursor itself, it can ask only to get extension events
from devices that will display a cursor, by passing the
GDK_EXTENSION_EVENTS_CURSOR value to
gdk_input_set_extension_events(). Otherwise, the application
must retrieve the device information using gdk_devices_list(),
check the has_cursor field, and,
if it is FALSE, draw a cursor itself when it receives
motion events.

Each pointing device is assigned a unique integer ID; events from a
particular device can be identified by the
deviceid field in the event structure. The
events generated by pointer devices have also been extended to contain
pressure, xtilt
and ytilt fields which contain the extended
information reported as additional valuators
from the device. The pressure field is a
a double value ranging from 0.0 to 1.0, while the tilt fields are
double values ranging from -1.0 to 1.0. (With -1.0 representing the
maximum tilt to the left or up, and 1.0 representing the maximum
tilt to the right or down.)

One additional field in each event is the
source field, which contains an
enumeration value describing the type of device; this currently
can be one of GDK_SOURCE_MOUSE, GDK_SOURCE_PEN, GDK_SOURCE_ERASER,
or GDK_SOURCE_CURSOR. This field is present to allow simple
applications to (for instance) delete when they detect eraser
devices without having to keep track of complicated per-device
settings.

Various aspects of each device may be configured.
The configuration of devices is queried using gdk_devices_list().
Each device must be activated using gdk_device_set_mode(), which
also controls whether the device's range is mapped to the
entire screen or to a single window. The mapping of the valuators of
the device onto the predefined valuator types is set using
gdk_device_set_axis_use(). And the source type for each device
can be set with gdk_device_set_source().

Devices may also have associated keys
or macro buttons. Such keys can be globally set to map
into normal X keyboard events. The mapping is set using
gdk_device_set_key().

The interfaces in this section will most likely be considerably
modified in the future to accomodate devices that may have different
sets of additional valuators than the pressure xtilt
and ytilt.

gdk_device_get_history ()

Obtains the motion history for a device; given a starting and
ending timestamp, return all events in the motion history for
the device in the given range of time. Some windowing systems
do not support motion history, in which case, FALSE will
be returned. (This is not distinguishable from the case where
motion history is supported and no events were found.)

Members

enum GdkInputSource

An enumeration describing the type of an input device
in general terms.

Members

GDK_SOURCE_MOUSE

the device is a mouse. (This will be reported for the core
pointer, even if it is something else, such as a trackball.)

GDK_SOURCE_PEN

the device is a stylus of a graphics tablet or similar device.

GDK_SOURCE_ERASER

the device is an eraser. Typically, this would be the other end
of a stylus on a graphics tablet.

GDK_SOURCE_CURSOR

the device is a graphics tablet "puck" or similar device.

enum GdkInputMode

An enumeration that describes the mode of an input device.

Members

GDK_MODE_DISABLED

the device is disabled and will not report any events.

GDK_MODE_SCREEN

the device is enabled. The device's coordinate space
maps to the entire screen.

GDK_MODE_WINDOW

the device is enabled. The device's coordinate space
is mapped to a single window. The manner in which this window
is chosen is undefined, but it will typically be the same
way in which the focus window for key events is determined.

struct GdkDeviceKey

struct GdkDeviceKey {
guint keyval;
GdkModifierType modifiers;
};

The GdkDeviceKey structure contains information
about the mapping of one device macro button onto a normal X key event.
It has the following fields: